Re: [PATCH] perf evsel: Adjust hybrid event and global event mixed group

From: Jiri Olsa
Date: Tue Jun 08 2021 - 06:57:09 EST

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On Tue, Jun 01, 2021 at 09:38:27AM +0800, Jin Yao wrote:
> A group mixed with hybrid event and global event is allowed. For example,
> group leader is 'intel_pt//' and the group member is 'cpu_atom/cycles/'.
>
> e.g.
> perf record --aux-sample -e '{intel_pt//,cpu_atom/cycles/}:u'
>
> The challenge is their available cpus are not fully matched. For example,
> 'intel_pt//' is available on CPU0-CPU23, but 'cpu_atom/cycles/' is
> available on CPU16-CPU23.
>
> When getting the group id for group member, we must be very careful.
> Because the cpu for 'intel_pt//' is not equal to the cpu for
> 'cpu_atom/cycles/'. Actually the cpu here is the index of evsel->core.cpus,
> not the real CPU ID.
>
> e.g. cpu0 for 'intel_pt//' is CPU0, but cpu0 for 'cpu_atom/cycles/' is CPU16.
>
> Before:
>
> # perf record --aux-sample -e '{intel_pt//,cpu_atom/cycles/}:u' -vv uname
> ...
> ------------------------------------------------------------
> perf_event_attr:
> type 10
> size 128
> config 0xe601
> { sample_period, sample_freq } 1
> sample_type IP|TID|TIME|CPU|IDENTIFIER
> read_format ID
> disabled 1
> inherit 1
> exclude_kernel 1
> exclude_hv 1
> enable_on_exec 1
> sample_id_all 1
> exclude_guest 1
> ------------------------------------------------------------
> sys_perf_event_open: pid 4084 cpu 0 group_fd -1 flags 0x8 = 5
> sys_perf_event_open: pid 4084 cpu 1 group_fd -1 flags 0x8 = 6
> sys_perf_event_open: pid 4084 cpu 2 group_fd -1 flags 0x8 = 7
> sys_perf_event_open: pid 4084 cpu 3 group_fd -1 flags 0x8 = 9
> sys_perf_event_open: pid 4084 cpu 4 group_fd -1 flags 0x8 = 10
> sys_perf_event_open: pid 4084 cpu 5 group_fd -1 flags 0x8 = 11
> sys_perf_event_open: pid 4084 cpu 6 group_fd -1 flags 0x8 = 12
> sys_perf_event_open: pid 4084 cpu 7 group_fd -1 flags 0x8 = 13
> sys_perf_event_open: pid 4084 cpu 8 group_fd -1 flags 0x8 = 14
> sys_perf_event_open: pid 4084 cpu 9 group_fd -1 flags 0x8 = 15
> sys_perf_event_open: pid 4084 cpu 10 group_fd -1 flags 0x8 = 16
> sys_perf_event_open: pid 4084 cpu 11 group_fd -1 flags 0x8 = 17
> sys_perf_event_open: pid 4084 cpu 12 group_fd -1 flags 0x8 = 18
> sys_perf_event_open: pid 4084 cpu 13 group_fd -1 flags 0x8 = 19
> sys_perf_event_open: pid 4084 cpu 14 group_fd -1 flags 0x8 = 20
> sys_perf_event_open: pid 4084 cpu 15 group_fd -1 flags 0x8 = 21
> sys_perf_event_open: pid 4084 cpu 16 group_fd -1 flags 0x8 = 22
> sys_perf_event_open: pid 4084 cpu 17 group_fd -1 flags 0x8 = 23
> sys_perf_event_open: pid 4084 cpu 18 group_fd -1 flags 0x8 = 24
> sys_perf_event_open: pid 4084 cpu 19 group_fd -1 flags 0x8 = 25
> sys_perf_event_open: pid 4084 cpu 20 group_fd -1 flags 0x8 = 26
> sys_perf_event_open: pid 4084 cpu 21 group_fd -1 flags 0x8 = 27
> sys_perf_event_open: pid 4084 cpu 22 group_fd -1 flags 0x8 = 28
> sys_perf_event_open: pid 4084 cpu 23 group_fd -1 flags 0x8 = 29
> ------------------------------------------------------------
> perf_event_attr:
> size 128
> config 0x800000000
> { sample_period, sample_freq } 4000
> sample_type IP|TID|TIME|PERIOD|IDENTIFIER|AUX
> read_format ID
> inherit 1
> exclude_kernel 1
> exclude_hv 1
> freq 1
> sample_id_all 1
> exclude_guest 1
> aux_sample_size 4096
> ------------------------------------------------------------
> sys_perf_event_open: pid 4084 cpu 16 group_fd 5 flags 0x8
> sys_perf_event_open failed, error -22
>
> The group_fd 5 is not correct. It should be 22 (the fd of
> 'intel_pt' on CPU16).
>
> After:
>
> # perf record --aux-sample -e '{intel_pt//,cpu_atom/cycles/}:u' -vv uname
> ...
> ------------------------------------------------------------
> perf_event_attr:
> type 10
> size 128
> config 0xe601
> { sample_period, sample_freq } 1
> sample_type IP|TID|TIME|CPU|IDENTIFIER
> read_format ID
> disabled 1
> inherit 1
> exclude_kernel 1
> exclude_hv 1
> enable_on_exec 1
> sample_id_all 1
> exclude_guest 1
> ------------------------------------------------------------
> sys_perf_event_open: pid 5162 cpu 0 group_fd -1 flags 0x8 = 5
> sys_perf_event_open: pid 5162 cpu 1 group_fd -1 flags 0x8 = 6
> sys_perf_event_open: pid 5162 cpu 2 group_fd -1 flags 0x8 = 7
> sys_perf_event_open: pid 5162 cpu 3 group_fd -1 flags 0x8 = 9
> sys_perf_event_open: pid 5162 cpu 4 group_fd -1 flags 0x8 = 10
> sys_perf_event_open: pid 5162 cpu 5 group_fd -1 flags 0x8 = 11
> sys_perf_event_open: pid 5162 cpu 6 group_fd -1 flags 0x8 = 12
> sys_perf_event_open: pid 5162 cpu 7 group_fd -1 flags 0x8 = 13
> sys_perf_event_open: pid 5162 cpu 8 group_fd -1 flags 0x8 = 14
> sys_perf_event_open: pid 5162 cpu 9 group_fd -1 flags 0x8 = 15
> sys_perf_event_open: pid 5162 cpu 10 group_fd -1 flags 0x8 = 16
> sys_perf_event_open: pid 5162 cpu 11 group_fd -1 flags 0x8 = 17
> sys_perf_event_open: pid 5162 cpu 12 group_fd -1 flags 0x8 = 18
> sys_perf_event_open: pid 5162 cpu 13 group_fd -1 flags 0x8 = 19
> sys_perf_event_open: pid 5162 cpu 14 group_fd -1 flags 0x8 = 20
> sys_perf_event_open: pid 5162 cpu 15 group_fd -1 flags 0x8 = 21
> sys_perf_event_open: pid 5162 cpu 16 group_fd -1 flags 0x8 = 22
> sys_perf_event_open: pid 5162 cpu 17 group_fd -1 flags 0x8 = 23
> sys_perf_event_open: pid 5162 cpu 18 group_fd -1 flags 0x8 = 24
> sys_perf_event_open: pid 5162 cpu 19 group_fd -1 flags 0x8 = 25
> sys_perf_event_open: pid 5162 cpu 20 group_fd -1 flags 0x8 = 26
> sys_perf_event_open: pid 5162 cpu 21 group_fd -1 flags 0x8 = 27
> sys_perf_event_open: pid 5162 cpu 22 group_fd -1 flags 0x8 = 28
> sys_perf_event_open: pid 5162 cpu 23 group_fd -1 flags 0x8 = 29
> ------------------------------------------------------------
> perf_event_attr:
> size 128
> config 0x800000000
> { sample_period, sample_freq } 4000
> sample_type IP|TID|TIME|PERIOD|IDENTIFIER|AUX
> read_format ID
> inherit 1
> exclude_kernel 1
> exclude_hv 1
> freq 1
> sample_id_all 1
> exclude_guest 1
> aux_sample_size 4096
> ------------------------------------------------------------
> sys_perf_event_open: pid 5162 cpu 16 group_fd 22 flags 0x8 = 30
> sys_perf_event_open: pid 5162 cpu 17 group_fd 23 flags 0x8 = 31
> sys_perf_event_open: pid 5162 cpu 18 group_fd 24 flags 0x8 = 32
> sys_perf_event_open: pid 5162 cpu 19 group_fd 25 flags 0x8 = 33
> sys_perf_event_open: pid 5162 cpu 20 group_fd 26 flags 0x8 = 34
> sys_perf_event_open: pid 5162 cpu 21 group_fd 27 flags 0x8 = 35
> sys_perf_event_open: pid 5162 cpu 22 group_fd 28 flags 0x8 = 36
> sys_perf_event_open: pid 5162 cpu 23 group_fd 29 flags 0x8 = 37
> ------------------------------------------------------------
> ...
>
> Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> ---
> tools/perf/util/evsel.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 4a3cd1b5bb33..a9cf615fe580 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -1581,6 +1581,15 @@ int __evsel__read_on_cpu(struct evsel *evsel, int cpu, int thread, bool scale)
> return 0;
> }
>
> +static int evsel_cpuid_match(struct evsel *evsel1, struct evsel *evsel2,
> + int cpu)
> +{

could this be better name:

evsel__match_other_cpu(struct evsel *evsel, struct evsel *other, int cpu)

> + int cpuid;
> +
> + cpuid = perf_cpu_map__cpu(evsel1->core.cpus, cpu);
> + return perf_cpu_map__idx(evsel2->core.cpus, cpuid);
> +}
> +
> static int get_group_fd(struct evsel *evsel, int cpu, int thread)
> {
> struct evsel *leader = evsel->leader;
> @@ -1595,6 +1604,26 @@ static int get_group_fd(struct evsel *evsel, int cpu, int thread)
> */
> BUG_ON(!leader->core.fd);
>
> + /*
> + * If leader is global event (e.g. 'intel_pt//'), but member is
> + * hybrid event. Need to get the leader's fd from correct cpu.
> + */
> + if (evsel__is_hybrid(evsel) &&
> + !evsel__is_hybrid(leader)) {
> + cpu = evsel_cpuid_match(evsel, leader, cpu);
> + BUG_ON(cpu == -1);
> + }
> +
> + /*
> + * Leader is hybrid event but member is global event.
> + */
> + if (!evsel__is_hybrid(evsel) &&
> + evsel__is_hybrid(leader)) {
> + cpu = evsel_cpuid_match(evsel, leader, cpu);
> + if (cpu == -1)
> + return -1;
> + }

why do we call BUG_ON on the first one and return -1 on the other?
they are equally bad no?

could you put that into separate function, like

cpu = evsel__hybrid_group_fd(evsel, cpu);

jirka

> +
> fd = FD(leader, cpu, thread);
> BUG_ON(fd == -1);
>
> --
> 2.17.1
>

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